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 Probability and Statistics Basic Probability and Statistics Math Forum

 August 3rd, 2011, 11:23 PM #1 Senior Member   Joined: Dec 2010 Posts: 233 Thanks: 0 Probability 1.Given that P(B)=1/2,P(B l A)=3/7, P(B l A' ) =2/3 Find P(A ? B) ,P( A U B ),P( A l B ) 2.If P( A l B )=3/10,P( B' l A ) =2/3,A and B are independent,find P(B),P(A U B),P(A' l B ). Please help me to solve the question step by step.I need help. August 4th, 2011, 03:22 AM   #2
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Re: Probability

Quote:
 Originally Posted by hoyy1kolko 1.Given that P(B)=1/2,P(B l A)=3/7, P(B l A' ) =2/3 Find P(A ? B) ,P( A U B ),P( A l B )
If you mean by P(B l A) the conditional probabilty , I can give you an answer.
We know that
P(A&#39 =P(B | A)P(A)+P(B|A&#39 (1-P(A))" />
So
}{P(B | A)-P(B | A&#39 }=\frac{1/2-2/3}{3/7-2/3}=7/10" />
then

also

and finally

What do you think ? August 4th, 2011, 09:34 PM #3 Senior Member   Joined: Dec 2010 Posts: 233 Thanks: 0 Re: Probability I still don understand about the part how do you come out the equation p(B)=P(B l A)P(A) + P(B l A' )P(A') and one part state that P(A ? B)=P(A)P(BlA) ,i don understand why.i need explanation. August 5th, 2011, 05:35 AM   #4
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Re: Probability

Hello, hoyy1kolko!

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[color=beige] .[/color] August 6th, 2011, 05:09 AM #5 Senior Member   Joined: Dec 2010 Posts: 233 Thanks: 0 Re: Probability Thank for the excellent explanation.I get it now!! i still need some help. Two transistors are chosen at random from a batch of transistor containing ninety good and ten defective ones. a)If at least one out of the two transistors chosen is defective,find the probability that both transistors are defective. This are the part that i can't solve in this question.I need help.and explanation. Tags probability Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Threads Thread Thread Starter Forum Replies Last Post hbonstrom Applied Math 0 November 17th, 2012 07:11 PM token22 Advanced Statistics 2 April 26th, 2012 03:28 PM naspek Calculus 1 December 15th, 2009 01:18 PM

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